This invention relates to a partially divided turbine housing for turbochargers and the like, and more particularly, to a radial inflow, volute turbine housing of the foregoing type particularly useful in turbocharger applications for use with internal combustion engines having divided exhaust manifolds. The novel partially divided turbine housing, particularly in such applications, provides increased efficiency of varying degrees dependent on the type, size and characteristics of the internal combustion engine with which it is matched and the equally matched degree of housing chamber division. Furthermore, such increased efficiency is most apparent in direct comparison with either the prior fully divided or the prior fully undivided turbine housing structures.
The general use of turbochargers for increasing the efficiency of internal combustion engines is well known. In broad terms, the turbocharger is in the form of a turbo compressor assembly wherein the compressor impeller supplies a pressurized flow of air to the cylinders of the engine and with proper calculation and matching, increases the efficiency of combustion of the engine to in turn increase the usable engine power received therefrom. The turbine wheels are most frequently driven by directing the flow of exhaust gases from the engine into the turbine housing of the turbocharger and through various housing chamber formations against the turbine wheel for driving the same.
Furthermore, it has been found that one of the more preferred types of turbine housings for use in turbochargers from the standpoint of both efficiency and convenience is that having radial inflow into a 360.degree. volute housing chamber. The turbine driving exhaust gases are fed into the volute housing chamber and progressively feed generally radially inwardly into the central turbine wheel location to rotate the turbine wheel which, in turn, rotates a compressor which feeds air to the engine cylinders. Due to the gradually decreasing radial cross section of the volute housing chamber, as portions of the exhaust gases flow inwardly into the turbine wheel so as to progressively reduce the quantity of flow, the velocity of flow of the exhaust gases is maintained and maximizes the energy transmitted to the turbine wheel.
Another important factor which must be considered in the selection and design of turbochargers for internal combustion engines wherein the turbochargers are driven by the engine exhaust gases involves the particular inherent manner of exhaust gas flow from the engine cylinders. Considering any individual cylinder of virtually any internal combustion engine, once the power stroke has taken place, the exhaust valve begins to open for expelling the exhaust gases from the cylinder into the exhaust manifold. Furthermore, at the initial opening of the exhaust valve the hot exhaust gases within the cylinder are at high pressure.
Consequently, as the exhaust valve begins to open releasing these high pressure hot gases, there is an initial, sharply defined surge wherein the major portion of the hot exhaust gases quickly flow or surge at high velocity into the exhaust manifold. Following, during the remainder of the period that the exhaust valve is open, the flow of exhaust gases from the cylinder is at relatively low velocity as compared to this initial surge, then being primarily caused by normal piston movement decreasing the volume of the cylinder. This means that the resulting flow of exhaust gases within an engine exhaust manifold is primarily in surges or pulses and not in the ideal constant or smooth velocity form for being fed to and driving the turbine wheel of a turbocharger.
Adding to the complexity of the considerations is the fact that internal combustion engines are, of course, of multiple cylinder design and frequently provided with divided exhaust manifolds directing the exhaust gases to a common turbocharger. This means that one side of the divided exhaust manifold will serve one bank of cylinders pulsating at different times and the other half of the exhaust manifold will serve the other bank of cylinders pulsating at different times. Considering that a common turbocharger is being used, the normal requirement would be to join the exhaust gas flows in the exhaust manifold halves at the turbocharger so that a single exhaust gas flow is directed into the turbine housing, but unless the pulses in the exhaust gas flow in each exhaust manifold half perfectly coincide, a high pressure pulse at one half can coincide with a low pressure period between pulses in the other half so as to greatly inhibit the overall flow of exhaust gases to the turbine housing and greatly reduce the efficiency of the turbocharger.
In order to eliminate this problem, various prior attempts have been made to minimize the effect thereof, that is, a high pressure pulse of one exhaust manifold half feeding into the low pressure period of the other exhaust manifold half inhibiting gas flows in each. For instance, certain prior turbocharger constructions have included a divider at the inlet into the turbine housing chamber of the turbocharger so as to extend or continue the division of the exhaust manifold halves into the initial portion of the turbine housing chamber and not attempt to mix the divided gas flows until initial housing gas flow patterns have been established. By arcuately shaping and blending the housing chamber inlet into the housing chamber proper and by terminating the divider at the commencement of the actual circumference of the housing chamber proper some slight improvements in exhaust gas flow have been made, while at the same time, according to the prior theories involved, not increasing the complexity of formation of the housing chamber proper, retaining it in its common volute form.
Major advances in solving the problem, however, have been made by not only providing a divider between the two gas flows at the turbine housing inlet portion, and particularly a radially extending divider, but continuing this radially extending divider completely around the total circumference of the turbine housing chamber. In other words, the turbine housing chamber is completely axially separated into two separate gas flow passages throughout the circumferential extent thereof, each separate gas flow passage progressively reducing in radial cross section in a normal volute manner and each communicating radially inwardly with the turbine wheel. Thus, by connecting the inlet of each of these separate housing chamber gas passages to the separate halves of the divided exhaust manifold of the engine, each acts as a separate unit generally independent of the other so that the effect of the pulses in each generally has no effect on the other, at least until the respective gas flows mix within the turbine wheel.
Although these fully divided turbine housings for turbochargers have provided, as stated, major advances in diminishing the effects of the discussed pulse problems within exhaust gas flows, it has been discovered that according to the principals of the present invention further unique refinements in turbine housings for turbochargers can be made which will produce markedly superior results and even further improve the efficiency of turbochargers as used with internal combustion engines.